Foam manufacture using two catalysts and a vaporizable auxiliary blowing agent

Abstract

A foam material, such as a polyurethane foam, is formed by mixing a polymer forming material with a blowing agent and two catalysts, one catalyst being provided to catalyze polymer formation and the other catalyst being provided to catalyze blowing. An auxiliary blowing agent in the form of a vaporizable substance, such as methylene chloride, is also incorporated. In one embodiment, the mixed components are maintained in a reaction vessel prior to application of same to a surface on which the foam is allowed to expand. In a further embodiment, in the case where the foam is polyurethane foam and the vaporizable substance is methylene chloride, the mixed components are maintained in a reaction vessel prior to application of same to a surface on which the foam is allowed to expand and the methylene chloride is used in an amount in excess of 12% of the weight of the polyurethane-forming material.

What I claim is: 
     
       1. A method of manufacturing a foam material comprising the steps of: mixing in a mixture head foam-forming components comprising: a blowing agent, polymer-forming material, first and second catalysts respectively for catalysing polymer formation with said polymer-forming material and blowing with said blowing agent, and an auxiliary blowing agent in the form of a vaporisable substance;   feeding said mixed components as a liquid from the mixing head to an open-topped reaction vessel wherein said components are maintained for a dwell time during which exothermic reaction occurs and the liquid froths; and   discharging said frothing liquid from the reaction vessel to a surface on which it is allowed to expand and form the foam material; the proportion of said first catalyst being reduced below the level required to achieve satisfactory foam formation without said dwell time.     
     
     
       2. A method of manufacturing foam polyurethane material comprising the steps of: mixing in a mixing head foam-forming components comprising: a polyol, an isocyanate, water, first and second catalysts respectively for catalysing polymer formation by intersecting on the polyol and the isocyanate and for catalysing blowing by intereaction of the isocyanate and the water, and methylene chloride as an auxiliary blowing agent;   feeding said mixed components as a liquid from the mixing head to an open-topped reaction vessel wherein said components are maintained for a dwell time of 20 to 45 seconds during which exothermic reaction occurs and the liquid froths; and   discharging said frothing liquid from the reaction vessel to a surface on which it is allowed to expand and form the foam material; the proportion of said methylene chloride being in excess of 12% of the weight of the polyol, and the proportion of said first catalyst being reduced below the level required to achieve satisfactory foam formation without said dwell time.   
     
     
       3. A method according to claim 2, wherein the polyol is a polyether glycol, the isocyanate is toluene diisocyanate, the first catalyst is an organo-metallic substance and the second catalyst is an amine compound. 
     
     
       4. A method according to claim 2 wherein the reaction vessel is an open-topped trough and the mixed components are fed to the bottom of the trough and are allowed to overflow from the top of the trough. 
     
     
       5. A method according to claim 4, wherein the overflowed material is directed down a ramp onto a moving conveyor. 
     
     
       6. A method according to claim 2 wherein the methylene chloride is fed into a conduit along which flows the polyurethane-forming material and a further component is fed under pressure into the conduit to effect vigorous mixing of the componenets in the conduit.